This invention relates to a tamper resistant seal made of a brittle material with internal defects internally arranged in a random pattern to form a unique fingerprint characteristic of the seal which may be identified by ultrasonic scanning to determine whether the seal has been replaced or otherwise altered and tampered with.
The prior art is replete with seals and other means for sealing containers and vessels containing dangerous chemicals, chemical warfare agents, radioactive wastes, and other hazardous materials which require special care and handling. When dealing with such materials security is obviously a matter of constant concern and much money, time, and effort has been devoted to prevent misappropriations or mishaps.
In one pertinent prior art approach, the seals have been made of an optical fiber and metal construction which has addressed the need for a cost efficient tamper proof security seal. Typically, these seals have been constructed to allow periodic inspection and surveillance to detect any breakage or unauthorized replacement of the seal. Such seals have been developed for the International Atomic Energy Agency to monitor compliance with the Treaty on Nonproliferation of Nuclear Weapons to ensure that nuclear materials are not diverted for nonpeaceful purposes. In one arrangement developed by the Sandia National Laboratory, a fiber optic passive flexible cable was developed that can be wrapped around a container and secured to an assembly in which a disrupted optic signal would indicate whether the cable fibers have been broken. More particularly, a unique pattern of transmitted light, set during the assembly process by cutting a set of fibers in a special way, permits identification and an integrity check by analysis of an optical pattern that is recorded on a computer disk.
Another fairly well known type of prior art seal utilizes wire and cup sealing device. In this arrangement, a wire is threaded through the item to be sealed and the bottom of the seal, which consists of a cup made from metal stampings. The ends of the wire are joined by a crimp-type or other device and sealed in the cup. A resin in the cup provides the unique fingerprint pattern.